Cartridge type mixing valves for hot and cold water incorporating a mixing unit made up of two overlapping disks in ceramic or other materials, one of which is fixed and the other movable, operated both radially and in rotation on and in respect to the fixed one, are already known. The fixed disk usually has two water inlet holes which communicate with two separate conduits for hot and cold water and an outlet hole leading to the tap to which the valve is fixed.
The moving disk is in turn operated by a control lever and the moving disk has a mixing chamber designed to selectively join one or both water inlet holes with the outlet one.
It has, however, not yet been possible to reach optimal flow and mixing results with the shapes of the water inlet holes or openings of the overlapping disks so far known, without having to adopt disks with relatively large diameters. This would mean that the volumes of the cartridge valves cannot be limited or contained as wanted.